Defibrillator discharge testing

Abstract

A variety of methods and discharge test circuits are described that are well suited for testing H-bridge based defibrillator discharge circuits. The H-bridge includes four switches and two outputs. In one aspect, a test discharge circuit is provided that includes a resistive element and a switch that are coupled to the second H-bridge output. The H-bridge and test circuit may be controlled to test various aspects of the H-bridge based defibrillator discharge circuit.

What is claimed is: 
     
       1. A defibrillator comprising:
 a shock discharge capacitor capable of temporarily storing and discharging sufficient energy to deliver a defibrillation shock to a patient; 
 an H-bridge having first, second, third and fourth switches, an input electrically coupled to the shock discharge capacitor, a first output configured to be electrically coupled to a first defibrillation electrode pad and a second output configured to be electrically coupled to a second defibrillation electrode pad; 
 a test discharge circuit including a test resistive element and a fifth switch, the test resistive element being electrically coupled between the fifth switch and the second output so that current passing between the second output and the second defibrillation electrode does not pass through the test resistive element, and so that electrical current passing through the fifth switch from the second output passes through the test resistive element; and 
 a controller configured to direct operation of the switches of the H-bridge in an operational mode to deliver a defibrillation shock, and to direct operation of the switches of the H-bridge and the test discharge circuit in a test mode to facilitate at least partially discharging the shock discharge capacitor internally within the defibrillator through the fifth switch and the resistive element; and 
 wherein in the test circuit is electrically coupled to the H-bridge so that the controller may direct at least a partial internal discharge of the shock discharge capacitor that passes through the test circuit and a single leg of the H-bridge. 
 
     
     
       2. A defibrillator as recited in  claim 1  wherein the controller is further configured to direct operation of the switches of the H-bridge and the test discharge circuit in a test mode to facilitate testing each of the H-bridge switches. 
     
     
       3. A defibrillator as recited in  claim 1  further comprising a first resistive element in a first electrical path between the shock discharge capacitor and the first H-bridge output that includes the first H-bridge switch, wherein the first resistive element is positioned so that:
 current passing through the first H-bridge switch also passes through the first resistive element; 
 current passing from the shock discharge capacitor through the second H-bridge switch does not pass through the first resistive element; and 
 no additional switches are required to prevent current passing through the second H-bridge switch from passing through the first resistive element. 
 
     
     
       4. A defibrillator as recited in  claim 1  wherein the resistance of the test resistive element is in the range of 100 to 10,000 ohms. 
     
     
       5. A defibrillator as recited in  claim 1  further comprising:
 the first and second defibrillation electrode pads; and 
 first and second relay elements, the first relay element being positioned in an electrical path between the first output and the first defibrillation electrode pad and the second relay element being positioned in an electrical path between the second output and the first defibrillation electrode pad. 
 
     
     
       6. A defibrillator as recited in  claim 5  further comprising a double pole double throw relay that includes the first and second relay elements. 
     
     
       7. A defibrillator as recited in  claim 1  wherein the at least partial internal discharge occurs through a path consisting essentially of the second switch, the test resistive element and the fifth switch. 
     
     
       8. A defibrillator comprising:
 a shock discharge capacitor capable of temporarily storing and discharging sufficient energy to deliver a defibrillation shock to a patient; 
 an H-bridge having first, second, third and fourth switches, an input electrically coupled to the shock discharge capacitor, a first output configured to be electrically coupled to a first defibrillation electrode pad and a second output configured to be electrically coupled to a second defibrillation electrode pad; 
 a test discharge circuit including a test resistive element and a fifth switch, the test resistive element being electrically coupled between the fifth switch and the second output so that current passing between the second output and the second defibrillation electrode does not pass through the test resistive element, and so that electrical current passing between the second output and the fifth switch passes through the test resistive element; 
 a controller configured to direct operation of the switches of the H-bridge in an operational mode to deliver a defibrillation shock, and to direct operation of the switches of the H-bridge and the test discharge circuit in a test mode to facilitate at least partially discharging the shock discharge capacitor through the fifth switch; and 
 a first resistive element in a first electrical path between the shock discharge capacitor and the first H-bridge output that includes the first H-bridge switch, wherein the first resistive element is positioned so that current passing through the first H-bridge switch also passes through the first resistive element, and current passing through the second H-bridge switch does not pass through the first resistive element, and no additional switches are required to prevent current passing through the second H-bridge switch from passing through the first resistive element. 
 
     
     
       9. A defibrillator as recited in  claim 8  wherein the resistance of the first resistive element is in the range of 1 to 10 ohms. 
     
     
       10. A defibrillator comprising:
 a shock discharge capacitor capable of temporarily storing and discharging sufficient energy to deliver a defibrillation shock to a patient; 
 an H-bridge having first, second, third and fourth switches, an input electrically coupled to the shock discharge capacitor, a first output configured to be electrically coupled to a first defibrillation electrode pad and a second output configured to be electrically coupled to a second defibrillation electrode pad; 
 a test discharge circuit including a test resistive element and a fifth switch, the test resistive element being electrically coupled between the fifth switch and the second output so that current passing between the second output and the second defibrillation electrode does not pass through the test resistive element, and so that electrical current passing between the second output and the fifth switch passes through the test resistive element; and 
 a controller configured to direct operation of the switches of the H-bridge in an operational mode to deliver a defibrillation shock, and to direct operation of the switches of the H-bridge and the test discharge circuit in a test mode to facilitate at least partially discharging the shock discharge capacitor through the fifth switch, and to cause a charging circuit to attempt to charge the shock discharge capacitor during a test phase with the second and fourth switches on and the first, third and fifth switches off. 
 
     
     
       11. A defibrillator comprising:
 a shock discharge capacitor capable of temporarily storing and discharging sufficient energy to deliver a defibrillation shock to a patient; 
 an H-bridge having first, second, third and fourth switches, an input electrically coupled to the shock discharge capacitor, a first output configured to be electrically coupled to a first defibrillation electrode pad and a second output configured to be electrically coupled to a second defibrillation electrode pad; 
 a test discharge circuit including a test resistive element and a fifth switch, the test resistive element being electrically coupled between the fifth switch and the second output so that current passing between the second output and the second defibrillation electrode does not pass through the test resistive element, and so that electrical current passing between the second output and the fifth switch passes through the test resistive element; and 
 a controller configured to direct operation of the switches of the H-bridge in an operational mode to deliver a defibrillation shock, and to direct operation of the switches of the H-bridge and the test discharge circuit in a test mode to facilitate at least partially discharging the shock discharge capacitor through the fifth switch, wherein the controller is configured to direct a test discharge by:
 causing the second and fifth switches to be on with the first, third and fourth switches off for a first test phase to cause the shock discharge capacitor to at least partially discharge through the test resistive element; 
 causing the second and fifth switches to be turned off when the shock discharge capacitor drains to a designated voltage; and 
 causing the first and third switches to be on for a second test phase with the second, fourth and fifth switches off after the shock discharge capacitor has drained to the designated voltage. 
 
 
     
     
       12. A defibrillator as recited in  claim 11  wherein the controller is further configured to cause a charging circuit to attempt to charge the shock discharge capacitor for a third test phase with the second and fourth switches on and the first, third and fifth switches off. 
     
     
       13. A method of testing a defibrillator discharge circuit that includes an H-bridge having first, second, third and fourth switches, an input electrically coupled to a shock discharge capacitor, a first output configured to be electrically coupled to a first defibrillation electrode pad, a second output configured to be electrically coupled to a second defibrillation electrode pad, and a first resistor in a first electrical path between the shock discharge capacitor and the first H-bridge output, the defibrillator discharge circuit being tested using a discharge test circuit that includes a fifth switch and a test resistor, the method comprising:
 causing the second and fifth switches to be on with the first, third and fourth switches off to cause the shock discharge capacitor to at least partially discharge through the second switch, the test resistor and the fifth switch during a first test phase; 
 turning the second and fifth switches off after the shock discharge capacitor reaches a designated voltage; and 
 causing the first and third switches to be on for a second test phase with the second, fourth and fifth switches off after the shock discharge capacitor has reached the designated voltage to further discharge the shock discharge capacitor through the first resistor and the first and third switches. 
 
     
     
       14. A method as recited in  claim 13  further comprising initiating charging the shock discharge capacitor for a third test phase with the second and fourth switches on and the first, third and fifth switches off. 
     
     
       15. A method of testing a defibrillator discharge circuit that includes an H-bridge having first, second, third and fourth switches, the method comprising:
 charging a shock discharge capacitor to a first designated voltage level suitable for delivering a defibrillation shock; 
 dissipating the charge on the shock discharge capacitor to a second designated voltage level through the second switch in a first test discharge phase, wherein the charging of the shock discharge capacitor and the first test discharge phase together expose the first, second, and third switches of the H-bridge to the designated voltage to test a dielectric strength of each of the first, second and third switches of the H-bridge; and 
 dissipating the charge on the shock discharge capacitor from the second designated voltage level through the first switch in a second test discharge phase. 
 
     
     
       16. A method as recited in  claim 15  wherein a peak current in the second test discharge phase exceeds 20 amps. 
     
     
       17. A method as recited in  claim 15  wherein during the second test discharge phase, dissipating current flows through both the first switch and the third switch. 
     
     
       18. A method as recited in  claim 15  further comprising initiating charging the shock discharge capacitor for a third test phase with the second and fourth switches on and the first, third and fifth switches off. 
     
     
       19. A method of reducing a charge on a defibrillator shock discharge capacitor in a defibrillator including the shock discharge capacitor and a discharge circuit that includes an H-bridge having first, second, third and fourth switches, an input electrically coupled to the shock discharge capacitor, a first output configured to be electrically coupled to a first defibrillation electrode pad and a second output configured to be electrically coupled to a second defibrillation electrode pad, the method comprising:
 turning a fifth switch on that is electrically connected to an effective ground and electrically connected to the second output via a resistive element; and 
 turning the second switch on after the fifth switch has been turned on with the first, third and fourth switches off to cause the shock discharge capacitor to at least partially discharge through a discharge path that includes the second switch, the resistive element and the fifth switch. 
 
     
     
       20. A method as recited in  claim 19  wherein the discharge path consists essentially of the second switch, the resistive element and the fifth switch. 
     
     
       21. A defibrillator comprising:
 a shock discharge capacitor capable of temporarily storing and discharging sufficient energy to deliver a defibrillation shock to the patient; 
 an H-bridge having first, second, third and fourth switches, an input electrically coupled to the shock delivery capacitor, a first output configured to be electrically coupled to a first defibrillation electrode pad and a second output configured to be electrically coupled to a second defibrillation electrode pad; 
 a first resistive element in a first electrical path between the shock discharge capacitor and the first H-bridge output that includes the first H-bridge switch, wherein current passing from the shock discharge capacitor to the first output through the first H-bridge switch also passes through the first resistive element and wherein current passing from the shock discharge capacitor to the second output through the second H-bridge switch does not pass through the first resistive element, and wherein the resistance of the first resistive element is greater than a total resistance between the shock discharge capacitor and the second H-bridge switch; and 
 a defibrillator controller configured to direct operation of the switches of the H-bridge in an operational mode to deliver a biphasic or multi-phasic defibrillation shock, wherein an initial phase of current for the defibrillation shock passes through the first H-bridge switch and the first resistive element and not the second H-bridge switch and a second phase of the defibrillation shock that follows the initial phase passes through the second H-bridge switch and not the first H-bridge switch and the first resistive element. 
 
     
     
       22. A defibrillator as recited in  claim 21  wherein no resistive elements are provided in a conductive path between the shock discharge capacitor and the second H-bridge switch. 
     
     
       23. A defibrillator comprising:
 a shock discharge capacitor capable of temporarily storing and discharging sufficient energy to deliver a defibrillation shock to the patient; 
 an H-bridge having first, second, third and fourth switches, an input electrically coupled to the shock delivery capacitor, a first output configured to be electrically coupled to a first defibrillation electrode pad and a second output configured to be electrically coupled to a second defibrillation electrode pad; 
 an H-bridge test circuit including a fifth switch electrically coupled between the H-bridge and an effective ground; and 
 a controller configured to direct operation of the switches of the H-bridge in an operational mode to deliver a defibrillation shock via the first and second outputs, and to direct operation of the switches of the H-bridge and the fifth switch in a test mode to internally discharge the shock discharge capacitor in a plurality of phases that utilize different discharge paths, wherein each internal discharge phase causes current to pass through at least one of the H-bridge switches and at least one of the internal discharge phases causes current to pass through the fifth switch in addition at least one of the H-bridge switches; and 
 wherein in the test mode, no switches other than one or more of the H-bridge switches and the fifth switch are activated during the multi-phase discharge test. 
 
     
     
       24. A defibrillator as recited in  claim 23  wherein the defibrillator controller is configured to cause the shock discharge capacitor to be charged to an operating voltage suitable for delivering the defibrillation shock in the test mode.